using System;
using System.IO;
using System.Text;
using FileHelpers.Helpers;
using FileHelpers.Options;

namespace FileHelpers.Dynamic
{
    /// <summary>Used to create classes that maps to CSV records (can be quoted, multiple lines, quoted, etc).</summary>
    public sealed class CsvClassBuilder : DelimitedClassBuilder
    {
        /// <summary>Creates a new DelimitedClassBuilder.</summary>
        /// <param name="className">The valid class name.</param>
        /// <param name="delimiter">The delimiter for that class.</param>
        /// <param name="sampleFile">A sample file from where to read the field names and number</param>
        public CsvClassBuilder(string className, char delimiter, string sampleFile)
            : this(new CsvOptions(className, delimiter, sampleFile)) {}

        /// <summary>Creates a new DelimitedClassBuilder.</summary>
        /// <param name="className">The valid class name.</param>
        /// <param name="delimiter">The delimiter for that class.</param>
        /// <param name="numberOfFields">The number of fields in each record.</param>
        public CsvClassBuilder(string className, char delimiter, int numberOfFields)
            : this(new CsvOptions(className, delimiter, numberOfFields)) {}

        /// <summary>Creates a new DelimitedClassBuilder.</summary>
        /// <param name="options">The specifications for the CSV file.</param>
        public CsvClassBuilder(CsvOptions options)
            : base(options.RecordClassName, options.Delimiter.ToString())
        {
            IgnoreFirstLines = options.HeaderLines;

            IgnoreEmptyLines = options.IgnoreEmptyLines;

            if (options.SampleFileName != string.Empty) {
                string firstLine = RawReadFirstLines(options.SampleFileName, 1);

                if (options.HeaderLines > 0) {
                    foreach (var header in firstLine.Split(options.HeaderDelimiter == char.MinValue
                        ? options.Delimiter
                        : options.HeaderDelimiter))
                        AddField(StringHelper.ToValidIdentifier(header));
                }
                else {
                    int fieldsNbr = firstLine.Split(options.Delimiter).Length;
                    for (int i = 0; i < fieldsNbr; i++)
                        AddField(options.FieldsPrefix + i);
                }
            }
            else if (options.NumberOfFields > 0)
                AddFields(options.NumberOfFields, options.FieldsPrefix);
            else {
                throw new BadUsageException(
                    "You must provide a SampleFileName or a NumberOfFields to parse a generic CSV file.");
            }
        }

        /// <summary>Add a new Delimited field to the current class.</summary>
        /// <param name="fieldName">The Name of the field.</param>
        /// <param name="fieldType">The Type of the field.</param>
        /// <returns>The just created field.</returns>
        public override DelimitedFieldBuilder AddField(string fieldName, string fieldType)
        {
            base.AddField(fieldName, fieldType);

            if (mFields.Count > 1) {
                LastField.FieldOptional = true;
                LastField.FieldQuoted = true;
                LastField.QuoteMode = QuoteMode.OptionalForBoth;
                LastField.QuoteMultiline = MultilineMode.AllowForBoth;
            }

            return LastField;
        }

        /// <summary>
        /// Adds to the class the specified number of fields.
        /// </summary>
        /// <param name="number">The number of fields to add.</param>
        public override void AddFields(int number)
        {
            AddFields(number, "Field");
        }

        /// <summary>
        /// Adds to the class the specified number of fields.
        /// </summary>
        /// <param name="prefix">The prefix used for the fields.</param>
        /// <param name="number">The number of fields to add.</param>
        public void AddFields(int number, string prefix)
        {
            int initFields = mFields.Count;

            for (int i = 0; i < number; i++) {
                int current = i + initFields + 1;
                AddField(prefix + current);
            }
        }

        private static string RawReadFirstLines(string file, int lines)
        {
            var sb = new StringBuilder(Math.Min(lines * 50, 10000));

            var reader = new StreamReader(file);

            for (int i = 0; i < lines; i++)
            {
                string line = reader.ReadLine();
                if (line == null)
                    break;
                else
                    sb.AppendLine(line);
            }
            reader.Close();

            return sb.ToString();
        }
    }
}